Transfection is the introduction of foreign material into eukaryotic cells using a vector as a means of transfer. The term transfection is most often used in reference to mammalian cells, while the term transformation is preferred to describe DNA transfer in bacteria and non-animal eukaryotic cells such as fungi, algae and plants.
Existing methods of transfection must overcome problems with the permeability of the cell membrane and the solubility of the transfected particle.
Drug delivery often involves transportation of the drug across cell membranes. The most basic method in vivo method is to introduce the drug into the blood stream by oral or intravenous methods and then hope it is absorbed by the correct cells. This non-discriminatory technique requires relatively large doses of the drug and simply does not work for some molecules such as DNA, which is used in gene therapy.
Existing methods to transfect material into a cell can be grouped into two categories: viral and non-viral. The utilization of viruses to transfect material into a cell has been shown to be extremely efficient; however, the possibility of a immune response to viruses and the insertion of mutagens into the body have proven to be serious concerns, especially in clinical trials. Non-viral drug delivery methods include naked DNA injection and electroporation. Unfortunately, naked plasmid DNA injection has shown to have a relatively low efficiency of gene delivery, while following electroporation tissue damage caused by the electric pulses has been observed.
Microinjection is a mechanical technique that utilizes a precision tool to place the molecule directly into the cell. This works excellently for DNA, however it is impractical in many situations as it can only be applied to one cell at a time.
A gene gun is a mechanical device that fires a particle bonded to the bio-molecule into the cell. These particles are relatively large and often damage cells. They also require large doses to be effective.
Electroporation is a physical method, which creates pores in the cell membrane by applying an electric shock to the cell. These pores allow the increased diffusion of materials into the cell. This increased permeability allows for easier transfection.
Sonoporation is similar to electroporation except it uses ultrasound to stimulate the cell membrane. The ultrasound also creates turbulence in the fluid surrounding the cell, which increases the rate of diffusion across the membrane.
Calcium phosphate transfection is a chemical method, which is very cheap. It uses calcium phosphate bonded to DNA. This molecule in some cases is able to transfect cells; however, this method is often ineffective and limited.
Viral delivery is a very effective method because viruses naturally are a carrier of genetic information and are very adept at entering cells. This makes them an obvious choice to help deliver DNA molecules into cells. However, the use of viral vectors is sometimes undesirable because of their immunogenicity and their potential mutagenicity. Furthermore, viral delivery is non-specific and can trigger side effects in the host.
Yet another method uses magnetic force and a molecular delivery vehicle to cross the cell membrane. A version of this method is described in United States Patent Application 2007/0231908 A1, and requires that the molecular delivery vehicle be oriented before it penetrates the biological membrane.
For most of the above methods, the effectiveness is extremely variable depending on the cell type being transfected. Some cells are known to be harder to transfect then others and these are usually the cells that hold the greatest reward.
Therefore, there is a need in the art for methods of transporting biomolecules and other molecules of interest into cells which mitigate the difficulties of the prior art.